Secondary throttle operator for two-stage carburetors



Feb. 11, 1958 SECONDARY THROTTLE OPERATOR FIOR TWO-STAGE CARBURETORS 2 Sheets-Sheet 1 Filed July 15, 1954 IN V EN TOR.

ATTORNEY Feb. 11, 1958 w. J. GLYNN 2,823,018

SECONDARY THROTTLE OPERATOR FOR TWO-STAGE CARBURETORS 6x INVENTOR. WILLIAM J. GLYNN ATTORNEY trite SECONDARY THROTTLE OPERATOR FOR TWO-STAGE CARBURETORS Application July 15, 1954, Serial No. 443,521 2 Claims. (Cl. 26123) This invention relates to a multi-stage carburetion system for internal combustion engines, particularly, of the automotive type.

In a multi-stage carburetion system, where the secondary throttle valve is controlled by means of a differential pressure motor device which responds to pressure differences in a mixture conduit or conduits, it has been found that, in some cases, the secondary throttle valve does not open at the proper time or rate in order to produce the second stage of operation without loss of power or other undesirable effects. For instance, where the secondary operating device is responsive to pressure conditions in the secondary mixture conduit anterior to the throttle therein, opening of the secondary throttle can not be initiated at all unless this throttle is made unbalanced so as to respond to intake manifold suction or is initially held slightly open, both of which conditions, of course, adversely affects the idling and part throttle operation of the engine.

According to the present invention, initiation of opening movement of the secondary throttle valve is effected by means of a mechanical connection or nudger between the primary and secondary throttle valves which serves to positively open the secondary throttle valve about 10 during the final part of the opening movement of the primary throttle valve or at such point in the opening of the primary throttle as it is desired to initiate second stage operation.

In the accompanying drawings which illustrate the in vention,

Fig. 1 is a side view, shown partly in section, of a multistage carburetor illustrating the invention, both throttles being shown fully closed. v

Figs. 2 and 3 show a detail in plan and elevation views, respectively, viewed from lines 2-2 and 3-3 of Fig. 1.

Fig. 4 is a side view showing the lower part of a carburetor embodying a slightly modified form of the invention, with the primary throttle valve at the point of initiating opening of the secondary throttle valve.

Fig. 5 is a side view showing the lower part of a carburetor as in Figs. 1 or 2, but with the primary throttle valve fully opened, while the secondary throttle valve is locked closed.

Fig. 6 is a view similar to Fig. 5, but showing the secondary throttle valve forced slightly opened by its interconnection with the primary throttle valve.

Fig. 7 is a diagrammatic view showing the parts as in Fig. 5 with the secondary throttle valve locked closed.

Fig. 8 is another diagrammatic view showing the secondary latch or lock removed and the secondary throttle slightly opened by its interconnection with the primary throttle, as in Fig. 6.

The carburetor shown consists of primary and secondary downdraft mixture conduits 10 and 11 having upper air inlet portions 12 and 13 and lower outlet portions 14 and 15 flanged for attachment to internal combustion engine intake manifold (not shown). The outlet portions are controlled, respectively, by primary and Patent 9 secondary throttle valves 16 and 17 mounted on shafts 18 and 19. Adjacent the mixture conduits are constant level fuel chambers 20 and 21 containing the usual float controlled mechanisms for maintaining fuel therein at a substantially constant level. In the bottoms of bowls 20 and 21 are metering orifice elements 22 and 23 through which fuel is supplied to upwardly inclined primary and secondary main fuel nozzles 24 and 25 discharging into venturi tubes 26 and 27 in the respective mixture conduits. Idling fuel is supplied through passage 28 and ports 29 adjacent the edge of primary throttle 16 when closed. An idling system may be omitted from the secondary side or may be provided, as desired. In the air inlet portion of primary conduit 10 is a choke valve 30 controlled by familiar thermo-suction type automatic choke control mechanism located in housing 31 mounted on the outside of the air inlet portion of the carburetor.

Loosely received on the near end of primary throttle shaft 18 in Figs. 1, 2, 3, 4, S, and 6 is a lever 32 having an outward, circumferential lug 33. A second, U-shaped member 34 has apertured ears 34a and 34b also loosely received on the end of shaft 18 and straddling lever 32 (Fig. 3). Member 34 has radial fingers 34c and 34d projecting from ear 34b which have, respectively, outward and inward lugs 34s and 34 (Fig. 2). A third lever 35 is rigidly received on shaft .18 immediately outwardly of aforementioned ear 34b and has a tangential finger 35a and a radial finger 3512 with an inward lug 350. A torsion spring 36 is received about shaft 18 between loose lever 32 and outer ear 34b of member 34 and has its ends hooked about inward lugs 34 and 350 so as to constantly urge these lugs apart and also urge opposite finger 35a against lug 34e. Thus, loose member 34 and lever 35 tend to move as a unit with throttle shaft 18. When primary throttle valve 16 is closed, lug 34e abuts lug 33 to urge loose lever 32 clockwise. When throttle 16 approaches its full open position, lug 34 engages notch 32a to urge lever 32 counterclockwise, as will be further described hereafter.

Loose lever 32 is connected by a link 37 to one arm of a bellcrank 38 rigid with the extremity of secondary throttle shaft 19. The other arm of this bellcrank is connected by a link 39 to a diaphragm 40 clamped be tween housing members 41 and 42 and forming a differ ential pressure motor therewith. The diaphragm is constantly urged to the right by a coiled compression spring 43 which normally urges secondary throttle valve 17 closed. Pressure chamber 44, to which the left-hand side of diaphragm 40 is exposed, is connected. by mean's'of passage 45, 46 to primary mixture conduit 10, substantially at the throat portion of outer venturi tube 47 therein. The right-hand side of diaphragm 40 is exposed to atmosphere through an opening 48 in casing 41. The arrangement of the differential pressure motor is such that as the velocity of air flow through venturi tube 47 increases, the pressure in motor chamber 44 decreases so that, ultimately, diaphragm 40 will be moved leftwardly against spring 43, opening secondary throttle valve 17.

However, tangential finger 35a on lever 35 rigid with the primary throttle valve cooperates with lug 34:; on member 34 and lug 33 on lever 32 to prevent opening of the secondary throttle in advance of the primary throttle and to positively close the secondary throttle when the primary throttle is closed. A lever 49 rigid with the primary throttle shaft has an aperture 50 for connection with the usual accelerator pedal in the drivers compartment. The usual throttle return spring (not shown) will be used to insure closing of the primary throttle valve when'pressure on the accelerator pedal is released.

The functioning of the interconnection between the primary and secondary throttle valves is better illustrated by the diagrammatic views in Figs. 7 and '8 which, in addition, show means to lock out the secondary throttle during starting when the choke valve is closed. In these figures, the reference numerals correspond to those in Fig. 1, except for those referring to parts modified for greater clarity of illustration, to which have been appended the letter X. In the diagrams, lever 35x formed rigid with primary throttle shaft 18 is extended, as at 49x, for attachment to the accelerator pedal linkage. This lever has a finger 350x which cooperates with loose lever 32x to positively close secondary throttle valve 17 when the primary throttle valve is closed. Connecting lever 35x on the primary throttle shaft and lever 38x rigid with the secondary throttle shaft is a oneway, resilient nudger connection including a sleeve 34x secured by means of a link 34xa to secondary throttle lever 38x and a-plunger 35bx secured by a link 35m to primary throttle lever 35x. Plunger 3517;: will be in the broken line position of Fig. 7 when both throttle valves are closed. As the primary throttle valve approaches its full open position, plunger 35bx engages a coiled compression spring 36x within sleeve 34x to yieldingly initiate opening of the secondary throttle valve, as in Fig. 8.

Figure 7 shows choke valve 30 closed and a latching link 55 dropped to interfere with an extension 38m on the secondary throttle shaft lever 38x to positively prevent opening of the secondary throttle. In order to permit full opening of the primary throttle, notwithstanding the functioning of this latch, spring 36x is compressed, as in Fig. 8. It will be understood, that spring 36x in Figures 7 and 8 corresponds with torsion spring 36 in Fig. 1.

The operation of the form in Fig. 1 is similar to that of the form shown diagrammatically in Figs. 7 and 8. As the primary throttle valve is opened, with the associated engine in operation, the velocity of air fiow through venturi tube 47 increases, causing a depression to be transmitted to the suction motor through passages 45, 46. Ultimately, the secondary throttle will be nudged slightly open by engagement of lug 34 with notch 32a in the edge of loose lever 32 connected to the secondary throttle (Fig. 6). Thereafter, further increase in the rate of air flow past passage 46 will cause diaphragm 40 to move leftwardly, continuing the opening of the secondary throttle. The initial nudging action mentioned has proven very important in insuring proper action of the secondary throttle due to the relatively small change in static suction to which the suction motor is exposed during secondary stage operation.

In case the'secondary throttle is locked closed when lug 34f abuts loose lever 32, as described, torsion spring 36 will yield permitting lever 35 and the primary throttle to continue the opening movement, as in Fig. 5.

In Figure 4, suction motor operating passage 45a communicates with the secondary mixture conduit, immediately anterior to the secondary throttle valve, instead of with the primary mixture conduit, as in Fig. 1. Other features of this form are the same as in the previous form and will not be further described. The primary throttle valve is shown approaching its full open position, with lug 34 on finger 34d just engaging lever 32 connected to the secondary throttle valve. Continued opening of the primary throttle will cause initial opening of the secondary throttle valve mechanically by its interconnection with the primary throttle valve, to expose motor operating suction passage 45a to air beginning to flow through the secondary conduit. When the velocity of this air reaches a sutlicient point, the differential pressure motor continues the opening movement of the secondary throttle, as in Fig. 1. As previously explained, the interconnection mechanism between the primary and secondary throttles operates the same in both forms.

The invention may be modified as will occur to those skilled in the art and the exclusive use of all modifications which come within the scope of the appended claims is contemplated.

I claim:

1. A two-stage carburetion system comprising primary and secondary mixture conduits having primary and secondary throttles, respectively, therein, a manual control for fully opening said primary throttle, a yielding operative connection between said throttles for partially opening said secondary throttle to initiate second-stage operation of the system responsive to final opening movement of said primary throttle, and an independent automatic control directly connected to said secondary throttle and responsive to variations of pressure in one of said conduits for opening said secondary throttle as the rate of air flow through the system increases for continuing opening movement of the secondary throttle after initial opening movement by said yielding operative connection.

2. A carburetion system as described in claim 1 in which a lost motion, two-way, operative connection is provided between said throttles to insure closing of said secondary throttle with said primary throttle and partial opening of said secondary throttle during opening movement of said primary throttle to initiate second stage operation of the system.

References Cited in the file of this patent UNITED STATES PATENTS 2,193,533 Kishline et al Mar. 12, 1940 2,390,019 Winkler et a1. Nov. 27, 1945 2,647,502 Braun Aug. 4, 1953 2,681,213 Gordon June 15, 1954 

